Which of the Following Is TRUE of the Reserve Clause

Which of the following is TRUE of the reserve clause?

A) While the reserve clause existed at the onset of professional sports leagues, it no longer exists in any form today.
B) The reserve clause allows players the opportunity to negotiate with other teams for higher pay and other incentives.
C) In North America, players must play a specified number of seasons according to the reserve clause and then qualify for free agency.
D) The reserve clause has been, and is, promoted by players' associations as most beneficial for professional athletes.